Electrode connecting pin



Filed April 3, 1948 BYQg R E l RB E N H ma R 0 I m v M ATTORNEY Patented Sept. 20, 1949 2,482,126

2,482,176 ELECTRODE conm-zc'rnvo rm Victor C. Hamister, Lakewood, Ohio, assignor to National Carbon Company, Inc., a corporation of New York Application April 3, 1948, Serial No. 18,732 1 Claim. (CI. 13-18) The invention relates tomembers used in joinplugs of the invention as electrode connecting ing carbon electrodes, including graphitized elecmembers. Data from these testsindicate thatthe trodes, particularly for use in electric'arc furhollow, slotted plug has the ability to absorb" naces. socket stresses and that its use as a connecting In order to provide a continuous feed of elec- 5 member between abutting electrodes resultsin a trode to a furnace, electrodes are drilled and tight joint with reduced socket strain. The holtapped at the end and joined by a threaded low, slotted plugis capable of withstanding severe nipple or plug of electrode material. thermal shock. Tests, in which the electrode Low resistivity across the interface between joint was surrounded by thermal insulation and joined electrodes is of great importance in modheated to 1700 C. by the passage therethrough on; em electric furnace practice due to the extremely large electric currents, and the joint subsequently high currents employed. This, together with the quickly chilled by removing the insulation, rerequirement for strength, has led to the use of sulted in no breakage at the electrode sockets ore--v solid threaded nipples or plugs as connecting of the hollow, slotted connecting plug. Furthermembers between electrodes. The use of solid more, electrical resistivity tests indicate that, due connecting members is not entirely satisfactory to the large area of the abutting interface at the and often results in electrode failure or breakage electrode ends, only an extremely minor increase as for example the splitting of electrodes at the in electrical resistivity at the joint results fromsocket during or after the connecting operation. the reduced cross sectional area of the hollow,

It is a primary object of the present invenslotted plug. tion to provide a connecting member for sectional In order to demonstrate further the advantages :i. electrodes capable of absorbing socket stresses of the connecting member of the invention, a" while retaining the low resistivity, high strength series of comparative tests were made in which and ability to withstand heat shock required of both solid plugs and hollow, slotted plugs of a size electrodes in modern industrial applications. so designed for use with 10 inch diameter electrodes In the drawing: were used as the connecting members for 8 inch Fig. 1 is a perspective view of one embodiment diameter electrodes. In these tests the socket of the connecting member of the invention shown walls of the 8 inch electrodes were considerablysa in position; thinner than normal and consequently much Fig. 2 is a sectional view taken along the line more sensitive to socket stresses. The plugs used 22 of Fig. 1; and were of the tapered shape illustrated in Fig. 1 and Fig. 3 is a sectional view taken along the line had a. maximum diameter of 8.66 inches at the 3-3 of Fig. 2.

Like numerals are used to designate like parts of 6.125 inches at the extremities. For purposes in all views. of the test twelve transverse strain gauges were Broadly, the invention comprises a connecting placed next to the socket face, one every 60 member for uniting the abutting ends of elecaround the circumference of each electrode. trodes, the connecting member being in the form In the joint assembly operation, torque was apof a hollow threaded nipple or plug having one or plied in 50 foot pound increments and measuremore longitudinal slots intermediate the ends 40 ments were taken of strain, electrical resistance thereof and extending through tne walls of said and travel. plug. The travel measured on the circumference of Referring to the drawing, Fig. 1 shows two the electrode upon the application of a torque tapped ends of electrodes I, I joined by a threadforce of 750 foot pounds was 1.00 inch for the ed, hollow, slotted plug member 3. A plurality of hollow, slotted plug as against 0.70 inch for the longitudinal slots 4, best seen in Figs. 2 and 3, solid plug. The 0.30 inch additional travel obextend through the walls and intermediate the tained by the use of the hollow, slotted plug indiends of plug 3. The end bore 5 of plug 3 may be cates that the hollow, slotted plug was comof such size as to provide a collar 6 at the ends pressed radially in the middle portion thus tendof slots 4 thus adding to the strength of the plug. ing to conform to the socket shape. The threads 1 may be of conventional design, no Comparative electrical resistivity measurealteration in their pitch being required because ments made upon joints using solid plugs and of the hollow, slotted construction of the plug. hollow, slotted plugs indicate only minor diifer- Many comparisontests have been made between ences at all pressur At 750 foot pounds the conventional solid plugs and the hollow, slotted o5 resistance across the Joint twins h Solid P l ,was 0.000031 ohms 750 foot pounds.

I duction of the maximum'strain from inch almost doubles :theiactor it is shown that the ohms for the hollow, slotted plug.

Data showing strain upon the socket wall after the assembly of electrodejoints with bothsolid and hollow, slotted plugs is shown in the table. I Joint assembly was The, torque force applied in Comparative strain in microi nches per inch on outer socket wall between ploying solid plugs and hollow, slotted plugs l Hollow Solid Percent 01 1 Plug gf g Solid Plug Average value oi 12 strain ga located at each 60 around circumference of electrodes at the electrode oint lace 460 352 75. 5 Maximum v ue irom above gauges 781 482 62.0

These data show that not only is a substantial reduction in average strain at the socket face obtained by using the hollow, slotted plug of the invention as the connecting member in electrode joints but also, and more important, the maximum strain was reduced by over one third the value obtained by using the conventional solid plug. Wi the strain before rupture somewhere near one thousand microinches per inch, the remicroinches per I of safety. The chances of cracking the socket walls are still further decreased by use of theholelectrode joints emas-compared with 0.000035 1 connecting members having low, slotted plug which exerts no larger outward force than the solid plug and additionally has no solid core to resist the socket walls under thermal stresses. V

From these data on travel, resistance and strain hollow, slotted plug when used as a connecting'member for electrodes acmember having the abutting ends 01' tapped complishes the objectives of the invention by provldlng a stron tight joint with reduced socket strain andhaying-theability to absorb socket stresses with no material increase in resistivity.

The invention is not limited to the preferred embodiment shown but embraces all electrode the general shape of bisymmetrical truncated cones having the hollow, slotted construction of the invention.

What is claimed is:

A threaded carbonaceous electrode connecting shape of bisymmetrical truncated cones joined at their bases for uniting the carbonaceous electrodes, of hollow construction and longitudinal slots, each lntermediate both the ends thereof and extending through the walls of said member, said slots being so disposed within said walls as to provide an annular collar at each end or said member.

VICTOR Q, HAMISTER.

REFERENCES CITED UNITED STATES PATENT said member being havin a plurality of Number Name Date 1,040,830 Williamson Oct. 8, 1912 1,287,678 Hall Dec. 17, 1918 1,467,060 Munning Sept. 4, 1923 ;1,743,888 Hamister Jan..14, 1930 1,850,515 Peltz Mar..22, 1932 FOREIGN PATENTS Number Country Date 6,984 Great Britain 1911 6,986 Great Britain 1911 197,638 v Great Britain Nov. 17, .1922 339,780 Italy Apr. 28, 1936 

